1. Field of the Invention
The present invention relates to a communication system and, more particularly, to a technique of performing mutual authentication of information concerning a new or additional function between a base station and a terminal station in the same system.
2. Description of the Related Art
IEEE 802.11 (ISO/IEC 8802-11: 1999(E) ANSUIEEE Std 802.11, 1999 edition) is known as one of the specifications for communication systems in which terminal stations and base stations mutually communicate with each other through wireless media. This specification defines medium access control (MAC) layer and physical (PHY) layer specifications.
The MAC layer specification defines an identification value which makes each terminal station in a system to identify a function that is used by each terminal station (or a function that can be used). When a given terminal station is to wirelessly communicate with another terminal station, this identification value is transmitted upon being written in a specific field in a transmission frame. A terminal station which has received this frame determines the function to be used on the basis of the identification information indicated by the specific field, and communicates with the remote terminal station on the basis of the function upon designating the function by frame exchange if needed.
In a conventional communication system complying with an existing specification such as IEEE 802.11, a given terminal station cannot notify, by communication, another terminal station of the possession of a function other than those defined in the specification, cannot recognize a notification concerning such an incompliant function from another terminal station, and cannot notify whether the incompliant function can be used or not.